Systemic corticosteroids inhibit bone healing in a rabbit ulnar osteotomy model

Prolonged systemic administration of corticosteroids causes osteoporosis and increased risk of fracture. Despite this well documented side effect of systemic corticosteroids, the effect of these compounds on fracture healing is not well defined. The goal of this study was to test the hypothesis that systemic corticosteroid therapy adversely affects fracture healing in a rabbit ulnar osteotomy model. Non-critical sized (1 mm) defects were created bilaterally in 18 adult female New Zealand White rabbits. Starting 2 months before operative intervention and continuing for 6 weeks during healing of the osteotomies, a subcutaneous dose of either sterile saline or prednisone (0.15 mg/kg) was administered daily. Serial radiographs of the forelimb were taken immediately postoperatively and weekly beginning the second week postoperatively. After killing at 6 weeks, only 3 of 20 limbs from animals treated with prednisone achieved radiographic union while 13 of 16 control limbs achieved union. The radiographic density of bone in the defect as well as callus size were greater in the control limbs than in the limbs from prednisone-treated animals. DEXA confirmed that the bone mineral content was lower in the ulnae of prednisone-treated rabbits both within the defect and in adjacent ulnar bone. Mechanical data indicated that osteotomies from rabbits chronically treated with prednisone were weaker than in controls. In this rabbit ulnar osteotomy model, chronic prednisone treatment clearly inhibited bone healing.     

Systemic corticosteroids inhibit bone healing in a rabbit ulnar osteotomy model

Prolonged systemic administration of corticosteroids causes osteoporosis and increased risk of fracture. Despite this well documented side effect of systemic corticosteroids, the effect of these compounds on fracture healing is not well defined. The goal of this study was to test the hypothesis that systemic corticosteroid therapy adversely affects fracture healing in a rabbit ulnar osteotomy model. Non-critical sized (1 mm) defects were created bilaterally in 18 adult female New Zealand White rabbits. Starting 2 months before operative intervention and continuing for 6 weeks during healing of the osteotomies, a subcutaneous dose of either sterile saline or prednisone (0.15 mg/kg) was administered daily. Serial radiographs of the forelimb were taken immediately postoperatively and weekly beginning the second week postoperatively. After killing at 6 weeks, only 3 of 20 limbs from animals treated with prednisone achieved radiographic union while 13 of 16 control limbs achieved union. The radiographic density of bone in the defect as well as callus size were greater in the control limbs than in the limbs from prednisone-treated animals. DEXA confirmed that the bone mineral content was lower in the ulnae of prednisone-treated rabbits both within the defect and in adjacent ulnar bone. Mechanical data indicated that osteotomies from rabbits chronically treated with prednisone were weaker than in controls. In this rabbit ulnar osteotomy model, chronic prednisone treatment clearly inhibited bone healing.     

Parathyroid hormone-related protein analog RS-66271 is an effective therapy for impaired bone healing in rabbits on corticosteroid therapy

A new class of parathyroid hormone-related protein (PTHrP) analogs has been developed that causes a rapid gain in both trabecular and cortical bone in models of osteopenia. This study investigates the efficacy of the PTHrP analog, RS-66271 ([MAP(1-10)]22-31 hPTHrP(1-34)-NH(2)), as systemic therapy for impaired bone healing in corticosteroid-treated rabbits. A 1 mm defect was created bilaterally in the ulnae of 30 rabbits. Delayed healing was induced by daily injections of prednisone (0.15 mg/kg) beginning 2 months prior to surgery and continuing until killing. Rabbits in the experimental group received daily subcutaneous injections of PTHrP analog RS-66271 (0.01 mg/kg) starting 1 day after surgery. Control animals received subcutaneous normal saline. At the 6 week timepoint, nine of ten ulnae from PTHrP-treated rabbits achieved radiographic union, whereas only two of ten limbs achieved union in control rabbits (p < 0.01). In a separate part of the study, 20 animals (10 control, 10 RS-66271-treated) were killed when radiographic union was achieved bilaterally. In this portion of the study, all limbs in animals treated with PTHrP achieved union by 6 weeks. In the control animals that were allowed to heal for 10 weeks, only 20% of the limbs achieved radiographic union. In addition, ulnae in the PTHrP-analog-treated rabbits showed greater radiographic intensity (20%-40%), larger callus area (209% anteroposterior view, 417% lateral view) (mean area on AP radiographs: control, = 387 +/- 276 mm(2); PTHrP analog, 1195 +/- 408 mm(2)), and greater stiffness (64%) and torque (87%) when compared with controls. RS-66271 was shown to be an effective therapy for preventing impaired bone healing caused by prednisone in a rabbit model.     

Recombinant human bone morphogenetic protein 2 enhances bone healing in an experimental model of fractures at risk of non-union

INTRODUCTION: Identification of patients at risk of developing non-union and institution of procedures preventing non-union could be attractive in routine fracture management. We investigated whether recombinant human bone morphogenetic protein (rhBMP-2) delivered in a hyaluronic acid carrier could prevent non-union development in an experimental non-union model, which simulates the clinical situation of open mid-tibial fractures. METHODS: Sixteen rabbits underwent a standard non-union operation comprising mid-tibial osteotomy, excision of periosteum and endosteum, and plate fixation. Before closure of the wound eight rabbits received interfragmentary deposition of 200 microg rhBMP-2 delivered in a hyaluronan gel carrier, and eight rabbits received gel carrier alone. RESULTS: After 7 weeks, torsional failure moment of the osteotomy and energy absorbed at failure, macroscopic and radiographic appearance, callus area, and interfragmentary bone volume fraction confirmed that rhBMP-2 delivery significantly improved bone healing. Blood flow at the osteotomy site, measured using radiolabelled microspheres, was not higher in the united osteotomies than in non-united osteotomies. DISCUSSION: rhBMP-2 delivered in a hyaluronic acid carrier-induced formation of competent bone in an experimental model of compromised healing. We, therefore, propose interfragmentary deposition of rhBMP-2 delivered in a hyaluronic acid carrier to patients encountering fractures at risk of non-union or delayed union.     

Effect of compression on fracture healing. Plate fixation studied in rabbits

Bilateral osteotomies in rabbit tibiae were secured with six-hole rigid plates, using axial compression on the right and no compression on the left side. Histological, histomorphometric and torsiometric analysis was performed up to 24 weeks postoperatively. Histological analysis showed end-to-end primary bone healing regardless of treatment. The fracture gaps tended to be smaller in the compression osteotomies, but union was achieved within the same time on both sides, and at 6 weeks torsiometric analysis of the paired specimens revealed similar mechanical properties. By the time the fracture had united both groups of bones showed similar degrees of subendosteal resorption. As a result of this porotic transformation the strength of the cortical bone was slightly impaired from 6 weeks onward, whether or not compression had been applied. The results suggest that axial compression does not augment fracture healing of plated cortical bone.     

Different healing patterns of experimental osteotomies treated by intramedullary nailing

Summary The healing of 52 diaphyseal osteotomies in rabbit tibiae was followed up histologically from 3 to 24 weeks after rigid intramedullary nailing. The histological evaluation was made from longitudinal sections through the osteotomy area. Particular attention was paid to the fracture healing pattern. A bulky periosteal response was visible in every specimen. At 24 weeks, the external callus was always well remodeled. The osteotomy line rapidly filled with bone from 6 weeks onwards. At 24 weeks, the site of osteotomy was detectable only on the basis of slight irregularity in the cortex. The secondary gap healing seen in 19 specimens was the most common type of bone union from 6 weeks onwards. In 13 specimens, the exact type of osteonal healing was not definable, since a solid union with good cortical reconstruction was always the final outcome. Altogether, four nonunions were detected throughout the study, none of these, however, in the specimens at 24 weeks. Considerable endosteal resorption was detected at 24 weeks, at which time at least one third of the original cortex had dissappeared in all specimens. The rigid nail seems to ensure a relatively uneventful healing of the experimental osteotomies. Vast endosteal resorption and some nonunions make the use of medullary reaming in this connection doubtful.     

Effect of preservation of corticoperiosteal attachment on bone healing at osteotomy sites after ulna-shortening osteotomy

Background

Although precise ulna-shortening osteotomy is popular, the procedure sometimes results in delayed union or nonunion. The periosteum including the inner cambium layer plays an important role in fracture healing. We tested the hypothesis that preservation of the corticoperiosteal attachment may accelerate healing at osteotomy sites after ulna-shortening osteotomy.

Methods

We performed a chart review of 32 patients who underwent ulna-shortening osteotomy for ulnar impaction syndrome or triangular fibrocartilage complex tears in a retrospective single-surgeon series. Of the 32 cases, the periosteum was preserved in 21 osteotomies performed from April 2009 onwards (periosteum-preserved group) and not preserved in 11 osteotomies performed before April 2009 (control group). Following sugar tong immobilization, patients in both groups used a short wrist supporter during the first two postoperative weeks (POW) and up to at least four POW. Union of the osteotomy site was assessed at 2-week intervals using radiographs taken at three different projections until 12 POW and at 4-week intervals thereafter until 24 POW. Ulna shortening was performed using a transverse osteotomy cut with the aid of a commercially available compression device.

Results

All osteotomies achieved complete union except in one case in the control group. The mean interval to complete cortical union was 7.7 weeks in the periosteum-preserved group and 9.5 weeks in the control group. The corresponding mean times for endosteal union were 15.6 and 21.8 weeks. The periosteum-preserved group had reduced times for both types of union but only the endosteal union time was significantly different from the control group.

Conclusions

Preservation of the corticoperiosteal attachment significantly shortened the endosteal union time. Our results indicate that preservation of the periosteum may accelerate bone healing after ulna-shortening osteotomy.     

The effect of ultrasound on bone healing across a bone gap,an experimental study of a delayed union model

The aim of the study is to determine whether ultrasound accelerates bone repair across a bone gap. To replicate the clinical situation of bone repair in a severe tibial fracture, such as Gustilo grade three, we designed an experimental model to determine whether ultrasound can promote bone healing in the presence of a bone gap. The effect of ultrasound on bone healing of a tibial bone gap held in an external fixator was studied. 60 New Zealand White rabbits were divided into four groups. In one group of 6 animals, a tibial osteotomy was closed or compressed and studied at six weeks (Comparative Group). In 3 groups of 18 animals each, a tibial bone gap was maintained and was untreated, treated with ultrasound or mock ultrasound (Control Group). The repair of the bone gaps was studied in 3 animals each at 2,4,6,8,10 and 12 weeks. Investigation was by histology, angiography, radiography and densitometry. Three of the 18 untreated group progressed to delayed union, compared with 4 in the ultrasound and 3 in the mock ultrasound group (Control Group). Statistical analysis showed no difference between the three groups. 5 of the 6 closed/compressed osteotomies (Comparative Group) united faster at 6 weeks. The healing pattern of the bone gap groups were similar. We recommend this as a delayed union model. We found no evidence that ultrasound accelerated bone healing, reduced the rate of delayed union or increased callus formation in this model of delayed union. This study simulates delayed union following a compound tibial fracture and has clinical relevance concerning treatment of a delay in union with ultrasound.     

Recombinant human bone morphogenetic protein-2 accelerates healing in a rabbit ulnar osteotomy model

BACKGROUND: Approximately 5% to 20% of fractures have delayed or impaired healing. Therefore, it is desirable to develop new therapies to enhance fracture-healing that can be used in conjunction with traditional treatment methods. The purpose of this study was to evaluate the ability of a single application of recombinant human bone morphogenetic protein-2 to accelerate fracture-healing in a rabbit ulnar osteotomy that heals spontaneously. METHODS: Bilateral mid-ulnar osteotomies (approximately 0.5 to 1.0 mm wide) were created in seventy-two skeletally mature male rabbits. The limbs were assigned to one of three groups: those treated with an absorbable collagen sponge containing recombinant human bone morphogenetic protein-2, those treated with an absorbable collagen sponge containing buffer, and those left untreated. In the first two groups, an 8 20-mm strip of absorbable collagen sponge containing either 40 g of recombinant human bone morphogenetic protein-2 or buffer only was wrapped around the osteotomy site. The rabbits were killed at two, three, four, or six weeks after surgery. In addition, twenty-four age-matched rabbits were used to provide data on the properties of intact limbs. The retention of recombinant human bone morphogenetic protein-2 at the osteotomy site was determined with scintigraphic imaging of (125)I-labeled recombinant human bone morphogenetic protein-2. After the rabbits were killed, the limbs were scanned with peripheral quantitative computed tomography to assess the area and mineral content of the mineralized callus. The limbs were then tested to failure in torsion, and undecalcified specimens were evaluated histologically. RESULTS: Gamma scintigraphy of (125)I-recombinant human bone morphogenetic protein-2 showed that 73% +/- 6% (mean and standard deviation) of the administered dose was initially retained at the fracture site. Approximately 37% +/- 10% of the initial dose remained at the site one week after surgery, and 8% +/- 7% remained after two weeks. The mineralized callus area was similar in all groups at two weeks, but it was 20% to 60% greater in the ulnae treated with recombinant human bone morphogenetic protein-2 than in either the ulnae treated with buffer or the untreated ulnae at three, four, and six weeks (p < 0.05). Biomechanical properties were similar in all groups at two weeks, but they were at least 80% greater in the ulnae treated with recombinant human bone morphogenetic protein-2 at three and four weeks than in either the ulnae treated with buffer (p < 0.005) or the untreated ulnae (p < 0.01). By four weeks, the biomechanical properties of the ulnae treated with recombinant human bone morphogenetic protein-2 were equivalent to those of the intact ulnae, whereas the biomechanical properties of both the ulnae treated with buffer and the untreated ulnae had reached only approximately 45% of those of the intact ulnae. At six weeks, the biomechanical properties were similar in all groups and were equivalent to those of the intact ulnae. The callus geometry and biomechanical properties of the ulnae treated with buffer were equivalent to those of the untreated ulnae at all time-points. CONCLUSIONS AND CLINICAL RELEVANCE: These findings indicate that treatment with an absorbable collagen sponge containing recombinant human bone morphogenetic protein-2 enhances healing of a long-bone osteotomy that heals spontaneously. Specifically, osteotomies treated with recombinant human bone morphogenetic protein-2 healed 33% faster than osteotomies left untreated. The results of this study provide a rationale for testing the ability of recombinant human bone morphogenetic protein-2 to accelerate healing in patients with fractures requiring open surgical management.     

The vascular repair of an experimental osteotomy held in an external fixator

The vascular repair of a lower tibial transverse osteotomy in the New Zealand white rabbit held in an external fixator was studied in three groups. In the first group, composed of 18 animals, the osteotomy gap was maintained throughout repair. Three animals were killed every two weeks up to 12 weeks postoperatively. In the second group, composed of three animals killed at six weeks, the fragments were brought into contact. In a third and similar group, the osteotomy was compressed. Plain roentgenograms were taken weekly, and intraarterial perfusion with Micropaque was performed when the animals were killed. Roentgenography using fine-grain film, microradiography, and histology were carried out on a midsagittal tibial slice. The results showed that following transverse osteotomy in which the gap was maintained, vascular union of the proximal and distal cortices and associated external callus masses had usually occurred by ten weeks postoperatively. However, an occasional hypovascular zone at the osteotomy site at 12 weeks was associated with fibrous delayed union. In contrast, when apposition or compression of the fragments was used, repair was accelerated, and cortical bone union was established at six weeks. Vascular union of the fragments occurred predominantly through the medullary vessels. The results emphasize the overriding clinical importance of abolition of a fracture gap to achieve rapid revascularization of a fracture and its union by bone.     

rhBMP-2 injected in a calcium phosphate paste (alpha-BSM) accelerates healing in the rabbit ulnar osteotomy model.

This study evaluated the ability of recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered in an injectable calcium phosphate carrier (alpha-BSM) to accelerate healing in a rabbit ulna osteotomy model compared to untreated surgical controls. Healing was assessed by radiography, histology and biomechanics. Bilateral mid-ulnar osteotomies were created in 16 skeletally mature rabbits. One limb in each animal was injected with either 0.1 mg rhBMP-2/alpha-BSM (BMP) (N=8) or buffer/alpha-BSM (BSM) (N=8). Contralateral osteotomies served as untreated surgical controls (SXCT). Gamma scintigraphy showed 75%, 45% and 5% of the initial 125I-rhBMP-2 dose was retained at the osteotomy site at 3 h, 1 week and 3 weeks. The biological activity of rhBMP-2 (alkaline phosphatase activity from bioassay) extracted from alpha-BSM incubated in vitro up to 30 days at 37 degrees C was unchanged. Radiographs demonstrated complete bridging of the BMP limbs at 4 weeks whereas none of the BSM or SXCT limbs were bridged. Post-mortem peripheral quantitative computed tomography determined mineralized callus area was 62% greater in BMP limbs compared to SXCT limbs. Torsional stiffness and strength were 63% and 103% greater in BMP limbs compared to SXCT limbs. There was no difference in torsional properties between BSM and SXCT limbs. Failure occurred outside the osteotomy in four out of seven of the BMP limbs. All BSM and SXCT limbs failed through the osteotomy. Histology showed bony bridging of the osteotomy and no residual carrier in the BMP limbs. BSM and SXCT groups showed less mature calluses composed of primarily fibrocartilaginous tissue and immature bone in the osteotomy gap. These data indicate rhBMP-2 delivered in alpha-BSM accelerated healing in a rabbit ulna osteotomy model compared to BSM and SXCT groups.     

海水浸泡开放性骨折伤愈合过程中组织病理学和血管内皮细胞生长因子(VEGF)表达

目的通过观察普通开放骨折、海水浸泡开放骨折愈合过程的组织学变化和骨痂中血管内皮细胞生长因子(VEGF)的表达,了解海水浸泡开放性骨折愈合过程VEGF的作用与机制。方法新西兰大白兔59只,随机分为普通开放骨折组(对照组)24只和海水浸泡开放骨折组(实验组)35只。造成桡骨横行1.5mm缺损完全开放骨折,普通开放骨折伤组旷置3h,海水浸泡开放骨折伤组海水浸泡伤口3h,之后依次缝合伤口。于第1、3、7、14、21、28、45天处死动物。观察海水浸泡开放骨折伤在骨折愈合中不同时间的病理过程。采用RT-PCR方法检测普通开放骨折、海水浸泡开放骨折不同阶段骨痂中的VEGF的表达及变化。结果海水浸泡开放骨折伤骨痂形成延迟,骨折后第28天,对照组断端间骨痂为骨性骨痂者8例,为软骨者4例,实验组断端间骨痂为骨性骨痂者6例,为软骨者14例。海水浸泡骨折伤愈合过程中新生骨痂的VEGF表达在骨折后逐渐升高,术后14d达到高峰,之后逐渐下降,但在28d时仍保持较高水平,与一般开放骨折愈合过程的VEGF表达无显著差异(P>0.05)。结论海水浸泡使骨折骨痂形成不良率增高,骨折愈合过程有延迟倾向;但骨折愈合过程中VEGF表达无明显变化。     

Recombinant human bone morphogenetic protein-2 enhances osteotomy healing in glucocorticoid-treated rabbits.

The objectives of this study were to evaluate the effect of chronic prednisolone treatment on osteotomy healing in rabbits and to determine whether recombinant human bone morphogenetic protein-2 (rhBMP-2) would enhance healing in the presence of chronic glucocorticoid therapy. Forty-nine skeletally mature, male rabbits were injected with either prednisolone (n = 26; 0.35 mg/kg per day, three times a week) or saline (n = 23). After a 6-week pretreatment period, bilateral ulnar osteotomies were created surgically. One osteotomy was treated with rhBMP-2 (0.2 mg/ml of rhBMP-2, 40 microg of rhBMP-2 total) delivered on an absorbable collage sponge (ACS), whereas the contralateral osteotomy remained untreated. Prednisolone or saline treatment was continued until the rabbits were killed either 6 weeks or 8 weeks after creation of the osteotomy. Osteotomy healing was evaluated by radiography, peripheral quantitative computed tomography (pQCT), torsional biomechanics, and undecalcified histology. Because we observed similar responses to both prednisolone and rhBMP-2/ACS treatment in the 6-week and 8-week cohorts, the results from these time points were combined. Serum osteocalcin and vertebral trabecular bone density were lower in the prednisolone-treated rabbits. Prednisolone treatment dramatically inhibited osteotomy healing. In the untreated ulnas, callus area and torsional strength were 25% and 55% less, respectively, in the prednisolone-treated rabbits than in the saline group (p < 0.001 for both). rhBMP-2/ACS enhanced healing in both the prednisolone- and the saline-treated groups, although the effect was larger in the prednisolone-treated rabbits. In the prednisolone-treated rabbits, callus area and torsional strength were 40% and 165% greater (p < 0.001 for both), respectively, in osteotomies treated with rhBMP-2/ACS compared with the contralateral, untreated osteotomies. Histological evaluation confirmed that osteotomy healing was inhibited by prednisolone and accelerated by rhBMP-2/ACS. In summary, a single application of rhBMP-2/ACS counteracted the inhibition of osteotomy healing caused by prednisolone exposure. These results suggest that rhBMP-2/ACS may be a useful treatment for enhancing fracture healing in patients who are undergoing chronic glucocorticoid therapy.     

组织隔离法与机械活动法在兔胫骨骨不连模型建立中的作用

目的 评价组织隔离法与机械活动法在建立兔胫骨萎缩型与肥大型骨不连模型中的作用方法将l2只体重为3～4．5kg的新西兰大白兔随机分成A、B两组，A组于胫骨中段截骨，两断端套接1cm硅胶管，单侧外固定器固定，保持两断端间距2mm，8周取出硅胶管，观察组织隔离法构建萎缩型骨不连模型的效果。B组于胫骨中段截骨后采用2枚1mm克氏针行髓内松动固定，被动活动断端200次／天，持续1个月，观察机械活动法构建肥大型骨不连模型的效果。结果 A组中所有动物在硅胶管取出后4周，无1例断端出现骨愈合表脱，X线片显示良好萎缩型骨不连的复制。B组中所有动物存6周内截骨端出现延迟愈合，部分伴有畸形．骨断端有人量肥大骨痂形成。结论 硅胶管组织隔离法是复制兔胫骨萎缩型骨不连模型的有效方法，而采用被动机械活动复制兔胫骨肥大型骨不连模型的方法尚需进一步研究。     

Indium-111 leukocyte scanning and fracture healing

This study was undertaken to determine the specificity of indium-111 leukocyte scans for osteomyelitis when fractures are present. Midshaft tibial osteotomies were performed in 14 New Zealand white rabbits, seven of which were infected postoperatively with Staphylococcus aureus per Norden's protocol. All 14 rabbits were scanned following injection with 75 microCi of indium 111 at 72 h after osteotomy and at weekly intervals for 4 weeks. Before the rabbits were killed, the fracture sites were cultured to document the presence or absence of infection. The results of all infected osteotomy sites were positive, whereas no positive scans were found in the noninfected osteotomies. We concluded from this study that uncomplicated fracture healing does not result in a positive indium-111 leukocyte scan.     

异体DBM复合rhBMP-2修复兔桡骨缺损的实验研究

目的探讨异体脱钙骨基质（demineralized bonematrix，DBM）复合重组人骨形态发生蛋白2（reconstruction humn bonemorphology protein-2，rhBMP-2）修复节段性骨缺损的能力。方法48只新西兰大白兔采用桡骨15mm节段性骨缺损模型，随机分为3组，A组植入异体DBM与rhBMP-2复合材料，B组植入异体DBM，C组为空白对照组。术后4周、8周、12周、16周．进行放射学和组织学检查。结果A组：术后4周宿主结缔组织长入植骨材料内的骨小梁间，并有岛状新生软骨、骨组织形成；术后8周，新生软骨及骨形成并融合成片；术后12周，新骨改建成熟，但仍能见到植骨材料；术后16周，管状骨结构形成，髓腔再通。B组：术后4周，植骨材料周围有软骨形成；术后8周，大量软骨形成；术后12周，大片状骨形成；术后16周，有髓腔形成。C组：各时问点仅见有纤维结缔组织，只在两端有新骨形成。X片示A组成骨量大，新骨改建、成熟迅速，术后16周全部达骨性愈合。B组成骨量少，仅2例达骨性愈合。C组未见骨性愈合。结论异体DBM复合rhBMP-2材料通过骨诱导和骨传导两种方式修复骨缺损，是一种较理想、具有高效成骨活性的植骨材料。     

Osteotomies of the fifth metatarsal.

Although the literature is limited primarily to retrospective small case series of the operative technique of fifth metatarsal osteotomies with a short follow-up, some important information can be learned. Stabilization of the osteotomy with Kirschner wire fixation appears to decrease dorsal displacement of the distal fragment and distal osteotomies; this leads to decreased incidence of transfer metatarsalgia. Kirschner wire fixation is advocated. The proximal chevron osteotomy of the fifth metatarsal, although stable, has a 20% delayed union rate, most likely resulting from the unique vascular anatomy in this region. The radiographic and clinical results appear to be compatible between distal and proximal osteotomies. Based on this information, primary use of a proximal osteotomy technique is not recommended. The oblique diaphyseal osteotomy technique requires an incision for the osteotomy as well as a distal incision at the metatarsophalangeal joint for correction of this joint. Hardware removal was performed in most patients, and the complications included two cases of delayed union. Time to healing was reported to be 8 weeks, 1.5 times the reported time to healing in distal chevron osteotomies. A significant radiographic correction was noted with the oblique diaphyseal osteotomy; however, radiographic measurements can be altered with foot position and lack of x-ray standardization and technique. Kitaoka et al found no correlation with the degree of radiographic correction and post-operative clinical symptoms. The authors agree with Kitaoka et al that the oblique diaphyseal osteotomy should be reserved for patients who fail an initial distal osteotomy technique. Distal oblique osteotomies appear to have less stability and more complications with malunion, transfer metatarsalgia, and delayed union and should be abandoned for a more stable chevron technique. The distal chevron osteotomy has a small incidence of transfer metatarsalgia; however, it appears to improve the clinical radiographic appearance of [table: see text] the foot with a shortened time to healing (4 to 6 weeks). A biplanar technique can be employed with a distal chevron osteotomy to improve plantar callosity symptoms. More studies are needed to examine critically patient outcomes with uniplanar and biplanar techniques using the distal chevron osteotomy.     

上肢骨干骨折内固定实验动物模型的建立

目的：建屯内固定术治疗上肢骨干骨折的实验动物模型，为研究不同内固定下骨折愈合的机制提供实验对象。方法：新西兰大白兔25只，随机选择一侧前肢上臂，取外侧切口显露肱骨，以线锯在其中段截骨，复位后植入天鹅记忆接骨器(SMC组)；同法在对侧植入4孔动力加压接骨板(DCP组)。分别在术后l、2、48、12周摄片观察骨折愈合情况，并处死5只动物取材，HE染色，行病理学观察。结果：术后动物全部成活，前肢负重明显低于后肢。X线片显示：SMC组在术后8周骨折愈合，愈合过程中未见明显外骨痂及板下皮质骨疏松；DCP组骨折愈合速度较慢，术后12周时骨折端仍有骨痂，伴局部皮质骨疏松。，病理学观察：术后8周，SMC组骨折端直接由板层骨替代；术后12周，DCP组形成骨性连接，处于改建塑形期。结论：SMC固定下实验性兔肱骨干骨折愈合过程与临床相似，愈合速度和质量优于DCP固定。兔肱骨干骨折内固定模型是一种较为理想的上肢骨干骨折内固定实验模型。     

Effect of repeated irrigation and debridement on fracture healing in an animal model.

The initial management of open fractures often requires repeated irrigation and debridement of the open wound and stabilization of the fracture. However, washing out the fracture hematoma could delay the early healing process of stable fractures. Because delayed union and non-union are serious complications, the effect of repeated irrigation and debridement on the fracture healing process was investigated. Twenty-four rabbits received unilateral, transverse. mid-tibial open osteotomies with a 3 mm gap. The osteotomy site was thoroughly irrigated and stabilized with double-bar external fixators. The osteotomy sites in the study groups underwent repeat irrigation and debridement on either the third day (Group II), the fourth day (Group III), or consecutively on the first and second days (Group IV) after the index procedure. The bone healing was assessed with weekly radiographs and peripheral quantitative computerized tomographs. In Group I (control), all osteotomies healed radiographically before the tenth week. In Group II, five out of six osteotomies healed radiographically before the tenth week. In Group III, only two of five osteotomies healed before the tenth week. In Group IV, none of the osteotomies had healed by week fifteen. All of the non-healed osteotomies exhibited atrophic non-unions at fifteen weeks. Compared to the control group at the tenth week, the average bone mineral content at the osteotomy site and the area of high mineral density callus (> or = 890 mg/cm3) were significantly lower in Groups III (63%, p = 0.002 and 95%, p = 0.05, respectively) and IV (99%, p < 0.001 and 100%, p = 0.05, respectively). The results of this study suggest that repeated irrigation and debridement, associated with persistent rigid immobilization, may contribute to the development of delayed unions or atrophic non-unions.     

Fixation of experimental osteotomy of the distal femur with biodegradable thread in rabbits

A distal femoral osteotomy on 24 rabbits was fixed with biodegradable polyglycolic acid (PGA) thread pulled through drill holes made on both sides of the osteotomy. Follow-up times were one, three, six, 12 and 24 weeks. The distal part of each femur was removed, fixed in alcohol, embedded in methylmethacrylate, sawed to 80 microns thick for oxytetracycline (OTC)-labeling studies and microradiography, and sectioned at 5 microns for histologic studies. As judged by histologic microradiographic, and OTC-labeling studies, 19 of 24 osteotomies were healing normally; after six weeks of follow-up examination, union of 11 of 14 osteotomies was observed on radiographs. On the basis of the present study, PGA threads may be promising for the fixation of osteotomies of the metaphyseal cancellous bone in rabbits.